docs: def generate_aead(hsm, args, password):
      """
      Generate an AEAD using the YubiHSM.
      """
      try:
          pw = password.ljust(args.min_len, chr(0x0))
          return hsm.generate_aead_simple(args.nonce.decode('hex'), args.key_handle, pw)
      except pyhsm.exception.YHSM_CommandFailed, e:
          if e.status_str == 'YHSM_FUNCTION_DISABLED':
              print "ERROR: The key handle %s is not permitted to YSM_AEAD_GENERATE." % (args.key_handle)
              return None
          else:
              print "ERROR: %s" % (e.reason)